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| Rio Grande riverbed south of Las Cruces in mid-May 2015 |
Just the previous week, the water was released from Caballo Dam and then, just upstream from Las Cruces, Leasburg Dam. That morning, I walked across the sandy riverbed. Dry like a child’s sandbox. There had been no flow through the channel since last October, unless one or two of the local rainstorms provided a brief flush of damp.
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| In the Rio Grande riverbed just north of Las Cruces, waiting for the flow to begin |
I watched the slow trickle of water as it approached us. Narrow rivulets covered with phosphorous soap foam built up during the dry months. As it grew to a wash, covered with four-inch-thick foam, we slowly moved out of the river bed. Backing away reluctantly. Craving the gurgling rush as we stood in 90-degree desert sun.
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| Walking to the east bank of the river as the water approaches |
This night on the river, one week later, we are riding our bikes swiftly along the path next to the Rio’s rush. Ducks cry out and flap wildly upward, silhouetted against the sunset. We hear frogs singing on all sides. A little foam still floats on the water, but the flow fills the riverbed and logs and clumps of grass also drift rapidly by.
The smells are strong and unlike the dry, desert odors we have noticed for months. It smells of life. Wet soil, algae, vegetation rotting anoxically in the wet.
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| The Rio in monsoon season, 2012, just south of Las Cruces |
The river before 1916
I think of the discussions of restoring flows for wildlife. Before 1916 and the construction of Elephant Butte Dam, the river flowed freely through the Mesilla Valley. It was a wild river, something like the Nile one imagines before Aswan High Dam, but without the tame expectations of consistently enriched fields.
In moments of heavy rainfall, the Rio Grande would radically change its course, swallowing houses, bursting through carefully cultivated fields and carrying away crops. Drowning people and animals. In dry times there was little relief. There was no way to save much water for irrigation through a difficult spell. Yet, this is the river the wild things knew.
The taming of the river made a far different agriculture possible. Crops grew with little fear they might wash away. Acequias stayed in place and were little damaged from year to year. Houses stayed put. The towns grew. In dry years, the stored water made all the difference.
Challenges to the river today
Even now, with the reservoirs hovering little above historic lows (lows like the massive 1950's drought), wells supplement the water allocated on the river and keep agriculture functioning. The eight acre-inches of river allotted to farmers is not enough for crops. But ever-deeper wells and pumps make growing possible. Pecans, for example, need three or four acre-feet every year, and they get it. With prices for pecans booming with Chinese demand, irrigating the trees makes financial sense.
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| Elephant Butte Reservoir Levels from 1915 to 2015. Graphic produced by and from data on U.S. Bureau of Reclamation site: http://www.usbr.gov/uc/crsp/GetSiteInfo |
On our recent bike ride, heading back toward Mesilla from the river, the damp smells remain, as we pass flooded pecan orchards. Then, as we approach the edge of town, the faint, desert smells replace the moisture in the air.
On a satellite map, the valley is a narrow thread of green running through the dun-yellow around it. The mountains east and west of the valley, thousands of feet higher, call the rain down on themselves. They, too, look green and abundant from the sky. Both greens may be deceptive. Both depend on precipitation patterns that are changing, and possibly changing for the long-term.
Predictions of a southwest mega-drought suggest that the reservoirs may often remain at least as low as they are now. Changing patterns in snowpack, for example, may increase the length of the dry season. The number of fires and stress on plants are likely to increase while water supplies falter.
Wild animals using the lower New Mexican Rio Grande are those who can currently survive a mere 70-day run of water every year. The river bed is dry most of the rest of the year. Some species are gone or endangered because of low water levels or other habitat threats.
The humans, too, are challenged. The expense of farming increases as more electricity or fuel is needed to pump from the aquifer. Some wells fill with sand as neighbors pump heavily, causing deep cones of depression at levels where the aquifer was once always full. Up in Hatch, chile production is threatened by the aquifer's salty water.
Running more water down the river is complicated. Not just by how little is available in the reservoirs, but also by obligations to Texas and Mexico. No more surface water can legally be allocated to farming without shorting neighbors to the south. Texas is challenging New Mexico in court, saying that groundwater pumping in the Mesilla Valley is impinging on Rio Grande Compact water that is due to Texas.
Water could be released down the stream at different times of year to help certain wild species, but with total water available so low, that might not make much difference. Moreover, more water would be lost to evaporation and absorption into the river bed if the release were more than once a year. This year alone, the Elephant Butte Irrigation District estimates that 30% or more of the water it runs in the river will be lost. The drier the year, the more dessicated the riverbed and the more it soaks up before sending water downstream.
Some flow of the river, of course, contributes to recharging the local aquifers. For the purposes of what they send on to Texas, though, engineers can only count what they can measure. And they measure dam levels, velocity in canals . . . but not water entering or being pumped from the aquifer.
The whole system is connected, with above- and below-ground flows being closely intertwined. For the humans, they are both accessible. For the rest of the fauna and for the flora, though, it is surface flow that matters most.
If drought continues, it is difficult to see an effective solution that grants water to both humans and wildlife. Adequate water even for humans alone may come into question over a long enough span, as with predicted mega-droughts. The aquifer, while very deep, is not limitless, and depends on surface replenishment.
The future of the Rio Grande as a wild river, as an agricultural river, is uncertain. A willingness to look for new ideas and new modes of using water will be increasingly important as the 21st century progresses.
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| Pecan orchards in the northern Mesilla Valley |
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| Farm-land in the Mesilla Valley south of Las Cruces: where the city leaves off, the farm-land begins. All of the deep green is pecan orchards. Doña Ana County, home to most of the Mesilla Valley, harvested 25,000 acres of pecans in 2013. The county is also a substantial producer of milk, cotton, and chiles. |
